Anisotropy of magnetic susceptibility (AMS) and rock magnetic data for Pachmarhi dyke swarm of Deccan

The Pachmarhi dyke swarms, situated in the Eastern part of the
Narmada-Satpura-Tapi (N-S-T) dykes of the Deccan Continental Flood Basalt
(DCFB), are studied using the Anisotropy of Magnetic Susceptibility (AMS)
technique. Here, we determine the direction and sense of magma flow within
the dykes to gain insights into the depth, number, and location of magma
chambers, as well as the geodynamics of their plumbing system. Petrography
and rock magnetism analyses revealed high-titanium magnetite particles,
predominantly of Pseudo-Single Domain (PSD) nature, with a smaller
proportion of Multi-Domain (MD) grains. We identified four distinct
magnetic fabric types (I-IV) within the Pachmarhi dykes. The imbrication
of magnetic foliation (for oblate fabric) and magnetic lineation (for
prolate fabric) has been employed to discern the direction of magma flow
which revealed multiple trends of magma flow, ranging from
vertical/sub-vertical to inclined, with one particular dyke exhibiting
lateral flow. The intersection of imbrication within the dyke margins
provided valuable information about the presence of multiple shallow
sub-crustal magma chambers which are supported by independent geophysical
evidence and are similar to those of the Nandurbar-Dhule dyke swarms in
the western region of the N-S-T dykes. Consequently, it can be inferred
that the emplacement of dykes in the Pachmarhi region of the NSL, which
were possible feeders to the late-stage Deccan volcanism, was primarily
facilitated by a "polycentric flow" mechanism, wherein magma was
injected vertically through shallow crustal fissures, potentially feeding
into the late-stage Deccan flow units like Ambenali or Mahabaleshwar
formation.